1. Field of the Invention
The present invention relates to a spread spectrum communication apparatus in which a spread spectrum signal obtained by performing a code division multiplex with orthogonal codes for transmission data is transmitted and the spread spectrum signal is received to reproduce the transmission data.
2. Description of the Related Art
To transmit data of a plurality of channels, a division multiplex is generally performed for the data. As a method of the division multiplex, a frequency division multiplex (FDM) method, a time division multiplex (TDM) method and a code division multiplex (CDM) method are well-known.
In the CDM method, a time-frequency-power space, in which orthogonal codes are spread, is divided into a plurality of sub-spaces corresponding to code channels along the power axis, an orthogonal transformation for data of each code channel is performed by using an orthogonal code spreading within one limited power zone of the time-frequency-power space, so that orthogonally-transformed transmission data is obtained for each code channel. Because a data rate and a weighting rate can be easily set for the transmission data for each code channel in the CDM method, this CDM method is appropriate for a hierarchical transmission.
In the CDM method used for a broadcasting field, a plurality of code channels are used for broadcast data, a weighting factor applied for the broadcasting data is set for each code channel, a broadcast signal is transmitted to a receiving side through each code channel, and the number of code channels, through which the broadcast signals added to each other on the receiving side are transmitted, is adjusted according to the quality of the broadcast signals received on the receiving side. Therefore, a graceful degradation for the broadcast data can be performed. A digital video signal transmission method performed in this graceful degradation has been studied for practical use.
In a mobile communication field, IS-95 method standardized as a code division multiple access (CDMA) cellular telephone system, in which a direct sequence (DS) type spread spectrum is used, is well-known. In this IS-95 method, code channels such as a control code channel and a communication code channel are used, control information and audio information are orthogonally coded with an orthogonal code in each code channel on a transmission side, the orthogonally coded information transmitted from the transmission side through one code channel is demodulated according to a communication procedure on a receiving side in a RAKE reception using a plurality of fingers, so that a communication quality for the control information and the audio information can be improved.
The RAKE reception is briefly described. The RAKE reception is a signal receiving processing peculiar to a spread spectrum communication method, and a path diversity reception can be performed in the RAKE reception.
In a digital communication such as a spread spectrum communication method, when a transmission signal is transmitted from a transmission side, a direct incoming wave directly incoming from the transmission side and a reflected wave transmitted from the transmission side while being reflected by buildings are generally received on a receiving side. In this case, because there are many paths for the reflected wave, a plurality of reflected incoming waves passing many transmission paths are received as a receiving signal on the receiving side. Therefore, a plurality of incoming waves, which each have a propagation delay time depending on the transmission path, are received on the receiving side. As a result, the incoming waves originated in the transmission signal interfere with each other, so that a receiving disturbance occurs on the receiving side.
However, in cases where a pseudo noise (PN) code used for the spread spectrum of the transmission signal is offset in point of time, a correlation among PN codes corresponding to various offsets (or phase offsets) is not obtained. This phenomenon that the correlation among the PN codes is not obtained is utilized to avoid the receiving disturbance occurring in a receiving signal composed of a plurality of incoming waves. In detail, in cases where a despread spectrum is performed for the receiving signal with a PN code in a despread spectrum unit of the receiving side after a phase offset corresponding to the propagation delay time of a particular incoming wave is given to the PN code, the despread spectrum is successfully performed only for the particular incoming wave, and the despread spectrum is not performed for the other incoming waves. Therefore, a despread spectrum can be selectively performed for each incoming wave without the interference of the incoming waves with each other by giving a phase offset corresponding to the propagation delay time of each incoming wave to the PN code.
Accordingly, in cases where a plurality of despread spectrum units are arranged in parallel to each other, a despread spectrum can be simultaneously performed for a plurality of incoming waves having different propagation delay times in the despread spectrum units by giving a phase offset corresponding to the propagation delay time of each incoming wave to the PN code in each despread spectrum unit, and a plurality of despread spectrum signals independent of each other can be obtained from the incoming waves.
The despread spectrum signals are weighted with weighting factors and are added to each other in an addition unit, so that a superior demodulated signal corresponding to the transmission signal can be obtained.
The spread spectrum signal receiving method described above is called a RAKE reception. Because a plurality of incoming waves of a receiving signal passing through different paths are selectively inverse-spread and are added to each other, the RAKE reception can be applied for a path-diversity reception.
Also, a W-CDMA method, in which a wide frequency band is used, is useful as a third generation type radio access method. In this W-CDMA method, a communication of audio data, video data and control data has been proposed by dividing the time-frequency-power space into a plurality of code channels in the code division multiplex.
3. Problems to be Solved by the Invention
In the digital video signal transmission method and the CDMA cellular telephone system described above, the number of code channels allocated to each user is generally fixed, and the incoming waves of the allocated code channels are demodulated in a demodulating unit of each user.
However, in the mobile communication field, though a service performing a high speed data transmission is required as well as a service mainly performing a low speed data transmission such as an audio data transmission, because the high speed transmission is performed in a conventional spread spectrum communication by heightening a data transmission rate for each code channel, there is a problem that an occupied zone for each code channel is increased. Therefore, it is difficult to perform the high speed data transmission in the conventional spread spectrum communication.
Also, conditions of each propagation path change with time in the mobile communication because of a selective fading and a non-selective fading occurring in the transmission signal and an interference between transmission signals of non-synchronized code channels, so that there is a problem that a communication quality for the receiving signal is degraded.
Also, to perform a data transmission based on the CDMA without widening a transmission band of each code channel, a data transmission method, in which a plurality of code channels are allocated to each user, is known. In this case, a degree of interference between the signals of the code channels is increased. Also, in cases where the number of code channels allocated to each user and a transmission electric power per code channel are adaptively changed or in cases where a plurality of code channels are used by a plurality of users, a degree of the interference is not stable, and it is required to hold the synchronization with each transmission signal even though the interference degree is changed. In addition, conditions of each propagation path change with time in the mobile communication because of a selective fading and a multipath fading occurring in the transmission signal and an interference between transmission signals of difference users, there is a problem that it is required to keep a signal electric power Eb/No standardized by a noise electric power No to a value more than a prescribed value for the purpose of holding a stable communication quality on the receiving side. Here, the symbol Eb denotes an energy per a bit.
In a radio communication system, an error control technique using a set of convolutional code and Viterbi decode or a set of error correcting code and Viterbi decode is mainly used to improve a communication quality. Also, the using of a Turbo code has been researched to obtain a higher coding gain, and the adopting of the Turbo code in the W-CDMA method has been examined. For example, in cases where the Turbo code is used in a static characteristic condition such as a white Gaussian noise (WGN) environment, it is reported that a superior characteristic such as a bit error rate (BER) less than 10xe2x88x925 is obtained even though a low signal electric power Eb/No less than 2 dB is set. However, in cases where a communication is performed at a low signal electric power such as Eb/No less than 2 dB, there is a problem that it is difficult to stably hold a synchronization with a receiving signal and to stably perform a phase detection for the transmission signal in a synchronized condition.
A first object of the present invention is to provide, with due consideration to the drawbacks of such a conventional spread spectrum communication apparatus, a spread spectrum communication apparatus in which a service of a high speed data transmission is performed without increasing an occupied band as well as a service mainly performing a low speed data transmission such as an audio data transmission.
A second object of the present invention is to provide a spread spectrum communication apparatus in which a service of a high speed data transmission is performed at a high quality in a low signal electric power (Eb/No) environment as well as a service mainly performing a low speed data transmission such as an audio data transmission while stably holding a synchronization with a transmission signal in the low signal electric power Eb/No environment and stably performing a phase detection for the transmission signal in a synchronized condition.
A third object of the present invention is to provide a spread spectrum communication apparatus, made of a coding apparatus using the Turbo code and a decoding apparatus, appropriate for an error control to perform a service of a high speed data transmission at a high quality as well as a service mainly performing a low speed data transmission such as an audio data transmission.
The first object is achieved by the provision of a spread spectrum communication apparatus comprising:
a spread spectrum signal transmitting apparatus for allocating a plurality of distinguishing codes to a plurality of code channels in one-to-one correspondence, producing a modulated symbol string from each of pieces of input data according to a data speed of the piece of input data, transforming each modulated symbol string with one distinguishing code allocated to one code channel to produce a piece of output data corresponding to the code channel for each code channel on condition that the piece of output data corresponding to each code channel is distinguishable from the pieces of output data of the other code channels according to the distinguishing codes, performing a spread spectrum for the pieces of output data of the code channels with a spread code sequence to produce spread output data, and transmitting the spread output data and channel information; and
a spread spectrum signal receiving apparatus for receiving the channel information from the spread spectrum signal transmitting apparatus and receiving the spread output data of the code channels transmitted from the spread spectrum signal transmitting apparatus as a receiving signal composed of a plurality of incoming waves transmitted through a plurality of propagation paths, the spread spectrum signal receiving apparatus comprising:
searching means for searching the receiving signal for a plurality of specific incoming waves of a specific code channel according to the channel information, detecting a plurality of receiving electric powers of the specific incoming waves and a plurality of phase offsets of the specific incoming waves to search the receiving signal for conditions of the propagation paths, and outputting a searcher detecting signal indicating the receiving electric powers of the specific incoming waves and the phase offsets of the specific incoming waves;
signal holding means for holding the receiving signal during an interference removing operation;
one or more finger units respectively having
inverse code transforming means for detecting a receiving electric power of a particular incoming wave, which corresponds to the specific code channel and a particular phase offset allocated to the finger unit, from the receiving signal directly received from the spread spectrum signal transmitting apparatus according to the channel information and the searcher detecting signal output from the searching means in the interference removing operation, specifying the spread code sequence and one particular distinguishing code corresponding to one particular code channel allocated to the finger unit according to the channel information, performing an inverse code transformation for the receiving signal with the particular distinguishing code and the spread code sequence in an interference-removed demodulating operation to produce an inversely code transformed signal from the output data of the particular code channel distinguished by the particular distinguishing code, and
demodulating means for demodulating the inversely code transformed signal produced by the inverse code transforming means to produce a finger demodulated symbol string of the particular code channel allocated to the finger unit;
interference electric power detecting means for selecting the specific code channel, of which the specific incoming waves have a high interference removing effect, from the code channels according to the channel information, receiving the particular incoming waves from the finger units, receiving the specific incoming waves from the searching means, determining a plurality of weighting factors corresponding to all specific incoming waves of the specific code channel according to the receiving electric powers of the particular incoming waves and a plurality of receiving electric powers of one or more specific incoming waves other than the particular incoming waves, weighting the particular incoming waves and the specific incoming waves other than the particular incoming waves with the corresponding weighting factors, and performing a despread spectrum for the particular incoming waves other than one particular incoming wave detected in one finger unit and the specific incoming waves other than the particular incoming waves detected by all finger units with the spread code sequence corresponding to the phase offset of each particular incoming wave or specific incoming wave to produce an interference replica signal corresponding to the finger unit for each of the finger units;
signal allocating means for allocating the receiving signal directly transmitted from the spread spectrum signal transmitting apparatus to the finger units in the interference removing operation and allocating an interference removed receiving signal, which is obtained by subtracting the interference replica signal corresponding to one finger unit from the receiving signal held by the signal holding means, to the finger unit as the receiving signal in the interference-removed demodulating operation for each of the finger units;
channel synthesizing means for synthesizing a demodulated symbol string from the finger demodulated symbol strings produced by the finger units;
decoding means for decoding the demodulated symbol string synthesized by the channel synthesizing means to reproduce the input data of the particular code channels allocated to the finger units; and
control means for controlling the finger units, the interference electric power detecting means and the signal allocating means according to the channel information and the conditions of the propagation paths detected by the searching means to allocate the particular code channel to each finger unit according to the channel information, allocate the particular phase offset detected by the searching means to each finger unit, transmit the receiving signal directly transmitted from the spread spectrum signal transmitting apparatus to the finger units in the interference removing operation and transmit the interference removed receiving signal produced by the interference electric power detecting means to the corresponding finger unit in the interference-removed demodulating operation for each of the interference-removed demodulating operation,
wherein, in cases where the allocation of one particular code channel to all finger units is indicated by the channel information, the same particular code string corresponding to the particular code channel is selected from the code strings in the finger units according to the channel information under the control of the control means to perform an inverse code transformation with the same particular distinguishing code in each of the finger units, the phase offsets corresponding to the specific incoming waves detected by the searching means are allocated to the finger units in the order of decreasing the receiving electric power of the specific incoming wave under the control of the control means, and the demodulation of a RAKE reception is performed in the finger units, and wherein, in cases where the allocation of a plurality of particular code channels to all finger units is indicated by the channel information, the particular distinguishing code corresponding to the particular code channel allocated to one finger unit is specified in the finger unit according to the channel information under the control of the control means for each of the finger units, a particular phase offset corresponding to the highest receiving electric power is selected from the phase offsets of the specific incoming waves detected by the searching means and is allocated to the finger units under the control of the control means, and the demodulations in the finger units are serially performed.
In the above configuration, spread output data of one or more code channels are transmitted from the spread spectrum signal transmitting apparatus to the spread spectrum signal receiving apparatus. Also, spread output data of a specific code channel (for example, a pilot channel) is output from the transmitting apparatus at a high electric power. Also, channel information indicating the specific code channel and one or more particular code channels to be allocated to the fingers of the receiving apparatus is transmitted from the transmitting apparatus to the receiving apparatus.
In the receiving apparatus, the spread output data is received as the receiving signal. In this case, because the spread output data pass through many propagation paths while being reflected by buildings, the receiving signal has a plurality of incoming waves corresponding to the propagation paths for each code channel. To search the receiving signal for conditions of the transmission paths, a plurality of receiving electric powers of specific incoming waves of the specific code channel and a plurality of phase offsets of the specific incoming waves are detected as a searcher detecting signal by the searching means.
Thereafter, an interference removing operation is performed under the control of the control means to perform an interference removing operation. In detail, the receiving signal transmitted from the spread spectrum signal transmitting apparatus is input to the finger units through the signal allocating means. Also, a particular code channel is allocated to each finger unit according to the channel information, and a particular phase offset detected by the searching means is allocated to each finger unit. In each finger unit, a receiving electric power of a particular incoming wave corresponding to the specific code channel and the particular phase offset is detected from the receiving signal. Thereafter, in the interference electric power detecting means, the specific code channel is selected from the code channels because the specific incoming waves of the specific code channel have a high interference removing effect, a plurality of weighting factors corresponding to all specific incoming waves of the specific code channel are determined according to the receiving electric powers of the specific incoming waves, the particular incoming waves and the specific incoming waves other than the particular incoming waves are weighted with the corresponding weighting factors, a despread spectrum is performed for the particular incoming waves other than one particular incoming wave detected in one finger unit and the specific incoming waves other than the particular incoming waves detected by all finger units with the spread code sequence, and an interference replica signal corresponding to the finger unit is produced for each of the finger units. The interference replica signal corresponding to one finger unit inversely influences on an inversely code transformed signal to be produced in the finger unit in an interference-removed demodulating operation as an interference signal.
In the interference-removed demodulating operation, the interference replica signal corresponding to each finger unit is subtracted from the receiving signal of the signal holding means by the signal allocating means to produce an interference removed receiving signal, and the interference removed receiving signal corresponding to one finger unit is transmitted to the finger unit for each of the finger units. In each finger unit, the particular distinguishing code corresponding to the particular code channel allocated to the finger unit is specified according to the channel information, an inverse code transformation is performed for the receiving signal with the particular distinguishing string and the spread code sequence to produce an inversely code transformed signal, and the inversely code transformed signal is demodulated to produce a finger demodulated symbol string. Thereafter, a demodulated symbol string is synthesized from the finger demodulated symbol strings corresponding to the finger units by the channel synthesizing means, and the demodulated symbol string is decoded by the decoding means to reproduce the input data.
Accordingly, because the phase offsets of the specific incoming waves of the specific code channel are detected by the searching means, the particular phase offset selected from the phase offsets can be accurately allocated to each finger unit. Also, because the receiving electric powers of the specific incoming waves of the specific code channel are detected by the searching means, the interference replica signal corresponding to each finger unit can be produced from the specific incoming waves of the specific code channel having the high interference removing effect, so that the specific incoming waves of the specific code channel most influencing on the demodulation of the receiving signal as an interference signal can be removed from the receiving signal by subtracting the interference replica signal from the receiving signal for each finger unit. Therefore, in cases where the demodulation of the RAKE reception is performed in the finger units because the same code channel is allocated to all finger units, the receiving signal can be demodulated at a high quality. Also, in cases where the demodulation of a plural code channel is performed in the finger units because a plurality of particular code channels allocated to all finger units are different from each other, the demodulations in the finger units for the particular code channels can be performed in parallel to each other at a high quality. That is, a service of a high speed data transmission is performed without increasing an occupied band as well as a service mainly performing a low speed data transmission such as an audio data transmission.
It is preferred that the channel information indicate an importance degree of each code channel, and the number of finger units, to which one particular code channel is allocated, depends on the importance degree of the particular code channel.
In this spread spectrum communication apparatus, the number of finger units corresponding to one code channel can be set according to the importance degree of the code channel.
It is also preferred that the channel information indicate an importance degree of each code channel, and it is judged by the control means whether or not the interference removing operation for one particular code channel allocated to each finger unit is performed according to the importance degree of the particular code channel.
In this spread spectrum communication apparatus, the interference removing operation can be performed for a particular code channel in cases where the control means judges the necessity of the interference removing operation according to the importance degree of the particular code channel.
It is also preferred that the interference removing operation for one finger unit be performed for each finger unit in cases where the control means judges, according to the channel information, the receiving electric powers of the particular incoming waves other than one particular incoming wave detected in the finger unit and the receiving electric powers of the specific incoming waves other than the particular incoming waves detected by all finger units, that the interference removing effect is high.
In this spread spectrum communication apparatus, the interference removing operation can be performed for each finger unit in cases where the interference removing effect is high.
It is also preferred that the control means obtain transmission electric powers of the piece of output data transmitted through the code channels and a multiplexing type performed for the pieces of output data in the spread spectrum signal transmitting apparatus from the channel information, the specific code channel having the highest interference removing effect is found out from the code channels according to the transmission electric powers of the piece of output data by the control means, and the interference replica signal is produced from the specific incoming waves of the specific code channel by the interference electric power detecting means.
In this spread spectrum communication apparatus, because the specific code channel having the highest interference removing effect is found out according to the transmission electric powers of the piece of output data, the interference removing operation can be performed according to the interference replica signal to perform the demodulation of the receiving signal at a high quality.
The first object is also achieved by the provision of a spread spectrum communication apparatus comprising:
a plurality of finger units respectively having
despread spectrum performing means for performing a despread spectrum for receiving data of one code channel allocated to the finger unit, and
inverse code transformation performing means for inversely performing a code transformation for the receiving data output from the despread spectrum performing means to produce a finger demodulated symbol string corresponding to the finger unit;
channel synthesizing means for synthesizing a demodulated symbol string from the finger demodulated symbol strings produced in the finger units;
interference replica signal prducing means for producing an interference replica signal functioning as an interference signal for the demodulation of the transmission data processed in one finger unit for each finger unit;
receiving signal storing means for storing a receiving signal in which pieces of receiving data of a plurality of code channels are included; and
signal allocating means for selecting the receiving data to be allocated to each finger unit from the receiving signal directly received from a transmitting apparatus in an interference removing operation, selecting the receiving data to be allocated to each finger unit from the receiving signal stored in the receiving signal storing means in a demodulating operation and allocating the receiving data to each finger unit in the interference removing operation and the demodulating operation, wherein
the interference removing operation and the demodulation of a RAKE reception performed in the finger units and the synthesizing of the demodulated symbol string performed by the channel synthesizing means are performed for each code channel, and the interference removing operation and the outputting of the receiving data read out from the receiving signal storing means to each finger unit through the signal allocating means are repeated until the pieces of receiving data of all code channels are demodulated.
In the above configuration, because the interference removing operation is performed, the demodulation of a RAKE reception can be performed at a high reliability for each code channel allocated to the finger units.
The second object is achieved by the provision of a spread spectrum communication apparatus comprising:
a spread spectrum signal transmitting apparatus for allocating a plurality of distinguishing codes to a plurality of code channels composed of one or more data channels and a pilot channel in one-to-one correspondence, producing a modulated symbol string from a piece of input data corresponding to a processing gain of a processing gain time-period according to a data speed of the piece of input data for each of pieces of input data, transforming each modulated symbol string with one distinguishing code allocated to one data channel to produce a piece of output data corresponding to the data channel for each data channel on condition that the piece of output data corresponding to each data channel is distinguishable from the pieces of output data of the other data channels according to the distinguishing codes, preparing a pilot signal composed of known data, transforming the pilot signal with the distinguishing code allocated to the pilot channel to produce a piece of output data corresponding to the pilot channel on condition that the piece of output data corresponding to the pilot channel is distinguishable from the pieces of output data of the data channels according to the distinguishing codes, and transmitting the pieces of output data of the code channels and channel information; and
a spread spectrum signal receiving apparatus for receiving the channel information from the spread spectrum signal transmitting apparatus and receiving the pieces of output data of the code channels transmitted from the spread spectrum signal transmitting apparatus as a receiving signal, the spread spectrum signal receiving apparatus comprising:
one or more finger units for respectively receiving the receiving signal transmitted from the spread spectrum signal transmitting apparatus and respectively demodulating the output data of one particular data channel included in the receiving signal according to the channel information transmitted from the spread spectrum signal transmitting apparatus;
decoding means for decoding the pieces of output data demodulated in the finger units to reproduce the pieces of input data of one or more particular data channels allocated to the finger units; and
control means for allocating the particular data channel to each finger unit according to the channel information transmitted from the spread spectrum signal transmitting apparatus, detecting the processing gain of the output data corresponding to the particular data channel allocated to each finger unit as a particular processing gain of each finger unit according to the channel information and controlling the finger units and the decoding means according to the channel information,
each finger unit comprising:
first inverse code transforming means for distinguishing the output data of the pilot channel from the other pieces of output data of the code channels with the distinguishing code allocated to the pilot channel according to the channel information and inversely performing a code transformation for the output data of the pilot channel to produce an inverse transformed pilot signal;
frequency error assuming means for assuming an original frequency error from the inverse transformed pilot signal produced by the first inverse code transforming means in a particular processing gain time period corresponding to the particular processing gain of the finger unit detected by the control means, outputting the original frequency error as frequency error assumption information in cases where the particular processing gain corresponding to the finger unit accords with a referential processing gain, assuming a referential frequency error in a referential processing gain time period of a referential processing gain from the inverse transformed pilot signal in cases where the particular processing gain corresponding to the finger unit is lower than the referential processing gain, comparing the original frequency error and the referential frequency error, outputting the referential frequency error as frequency error assumption information in cases where the original frequency error is larger than the referential frequency error, and outputting the original frequency error as frequency error assumption information in cases where the original frequency error is equal to or smaller than the referential frequency error;
synchronization holding means for producing a synchronization timing signal, which is synchronized with the output data of the pilot channel distinguished by the first inverse code transforming means, according to the frequency error assumption information output from the frequency error assuming means;
second inverse code transforming means for distinguishing the output data of the particular data channel allocated to the finger unit from the other pieces of output data of the code channels with the distinguishing code allocated to the particular data channel according to the channel information and inversely performing a code transformation for the output data of the particular data channel to produce an inverse transformed data signal; and
demodulating means for demodulating the inverse transformed data signal produced by the second inverse code transforming means, while holding a synchronization with the inverse transformed data signal according to the synchronization timing signal produced by the synchronization holding means, to produce a finger demodulation symbol corresponding to the finger unit, the finger demodulation symbol demodulated in the finger units being decoded by the decoding means.
In general, in cases where noises or fading in a propagation path between the transmitting apparatus and the receiving apparatus change with time, a frequency error changing with time occurs in the receiving signal. Therefore, it is difficult to hold a synchronization with the receiving signal in the receiving apparatus. In the present invention, the frequency error occurring in the pilot signal composed of known data is always detected in a processing gain time period of a processing gain of output data corresponding to a data channel allocated to each finger unit, and the output data is demodulated while holding the synchronization with the output data according to the detected frequency error.
However, in cases where the change of noises or fading in the propagation path is large, because the frequency error greatly irregularly changes with time, it is difficult to stably holding the synchronization with the output data. One reason that the frequency error occurs in the propagation path is a Doppler frequency (about 100 Hz) based on the Doppler effect in a mobile communication. Because a data rate in a high speed data transmission is more than 1 Mbps and because a data rate for each code channel is more than several tens Kbps, the data rate is greatly higher than the Doppler frequency. Also, noises in the propagation path are regarded as the white Gaussian noise. Therefore, it is better to detect the frequency error occurring in the pilot signal in a referential processing gain time period longer than the processing gain time period corresponding to the output data, so that the synchronization with the output data can be stably held. Here, a referential processing gain is largest among various processing gains, and the referential processing gain time period of the referential processing gain is longest among various processing gain time periods of the processing gain time periods.
In the above configuration of the spread spectrum communication apparatus, an inverse transformed pilot signal is produced from the output data of the pilot channel by the first inverse code transforming means, and an original frequency error of the output data of the pilot channel is assumed from the inverse transformed pilot signal, in the frequency error assuming means, in a particular processing gain time period corresponding to a particular processing gain of output data of a particular code channel allocated to a corresponding finger unit. Thereafter, in cases where the particular processing gain accords with a referential processing gain, the original frequency error is output as frequency error assumption information regardless of whether the change of noises or fading in a particular propagation path corresponding to both the output data of the pilot channel and the output data of the particular code channel is large.
In contrast, in cases where the particular processing gain corresponding to the finger unit is lower than the referential processing gain, a referential frequency error is assumed from the inverse transformed pilot signal, in the frequency error assuming means, in a referential processing gain time period of a referential processing gain, the original frequency error and the referential frequency error is compared each other. In cases where the original frequency error is larger than the referential frequency error, because the change of noises or fading in the particular propagation path is large, the referential frequency error is output as frequency error assumption information. In contrast, in cases where the original frequency error is equal to or smaller than the referential frequency error, because the change of noises or fading in the particular propagation path is small, the original frequency error is output as frequency error assumption information.
Thereafter, a synchronization timing signal synchronized with the output data of the pilot channel is produced according to the frequency error assumption information in the synchronization holding means, an inverse transformed data signal, which is produced from the output data of the particular data channel allocated to the corresponding finger unit in the second inverse code transforming means, is demodulated by the demodulating means while holding a synchronization with the inverse transformed data signal according to the synchronization timing signal, so that a finger demodulation symbol is produced. Thereafter, the finger demodulation symbols obtained in the finger units are decoded by the decoding means, so that the pieces of input data of one or more particular data channels allocated to the finger units are reproduced.
Accordingly, because the frequency error assumption information is produced from the pilot signal possible to be transmitted at a high electric power, the frequency error assumption information can be reliably obtained even though input data of the data channels are transmitted in the low signal electric power Eb/No environment. Also, because a synchronization timing signal is produced from the frequency error assumption information and because the output data of the data channels allocated to the finger units are reproduced according to the synchronization timing signal, a service of a high speed data transmission can be performed at a high quality in a low signal electric power (Eb/No) environment as well as a service mainly performing a low speed data transmission such as an audio data transmission while stably holding a synchronization with the output data of the code channels allocated to the finger units in the low signal electric power Eb/No environment and stably performing a phase detection for the output data in a synchronized condition.
Also, even though a particular processing gain of the output data of the code channel allocated to each finger unit is lower than a referential processing gain, because frequency error assumption information is produced according to a frequency error assumed in a referential processing gain time period of a referential processing gain of the referential processing gain in cases where the change of noises or fading in the particular propagation path is large, the output data of the particular processing gain lower than the referential processing gain can be demodulated while stably holding a synchronization with the output data of the code channels allocated to the finger units and stably performing a phase detection for the output data in a synchronized condition.
It is applicable that the finger units be classified into one first finger unit and one or more second finger units on condition that the particular processing gain of the output data allocated to the first finger unit is smaller than those of the pieces of output data allocated to the second finger units, the outputting of the frequency error assumption information be performed in the frequency error assuming means of the first finger unit, the outputting of the frequency error assumption information be not performed in the frequency error assuming means of each second finger unit under the control of the control means, a second original frequency error be assumed from the inverse transformed pilot signal produced by the first inverse code transforming means in a second particular processing gain time period corresponding to the particular processing gain of each second finger unit in the frequency error assuming means of the first finger unit, the second original frequency error be output as second frequency error assumption information in cases where the particular processing gain corresponding to the second finger unit accords with the referential processing gain, the second original frequency error and the referential frequency error be compared each other in cases where the particular processing gain corresponding to the second finger unit is equal to or lower than the referential processing gain, the referential frequency error be output as second frequency error assumption information in cases where the second original frequency error is larger than the referential frequency error, the second original frequency error be output as second frequency error assumption information in cases where the second original frequency error is equal to or smaller than the referential frequency error, a second synchronization timing signal be produced by the synchronization holding means of the first finger unit according to the second frequency error assumption information, and the inverse transformed data signal produced by the second inverse code transforming means of the second finger unit be demodulated by the demodulating means of the second finger unit while holding a synchronization with the inverse transformed data signal according to the second synchronization timing signal to produce a finger demodulation symbol corresponding to the second finger unit.
In this spread spectrum communication apparatus, in cases where the particular processing gain of the output data allocated to the first finger unit is smaller than those of the pieces of output data allocated to the second finger units, the second synchronization timing signal to be used for each second finger unit is produced by the synchronization holding means of the first finger unit. Therefore, the demodulating operation performed in the demodulating means of the second finger unit can be performed without producing the frequency error assumption information or the synchronization timing signal in both the frequency error assuming means and the synchronization holding of the second finger unit.
It is also applicable that the finger units be classified into one first finger unit and one or more second finger units on condition that the particular processing gains of the pieces of output data allocated to the first finger unit and the second finger units are the same as each other, the outputting of the frequency error assumption information be performed in the frequency error assuming means of the first finger unit, the outputting of the frequency error assumption information be not performed in the frequency error assuming means of each second finger unit under the control of the control means, and the inverse transformed data signal produced by the second inverse code transforming means of the second finger unit be demodulated by the demodulating means of the second finger unit while holding a synchronization with the inverse transformed data signal according to the synchronization timing signal produced by the synchronization holding means of the first finger unit to produce a finger demodulation symbol corresponding to the second finger unit.
In this spread spectrum communication apparatus, in cases where the particular processing gains of the pieces of output data allocated to the first finger unit and the second finger units are the same as each other, the synchronization timing signal produced by the synchronization holding means of the first finger unit is used in the demodulating means of each second finger unit. Therefore, the demodulating operation performed in the demodulating means of the second finger unit can be performed without producing the frequency error assumption information or the synchronization timing signal in both the frequency error assuming means and the synchronization holding of the second finger unit.
It is also preferred that each finger unit further comprises:
integration dump means for performing an integration dump, in which the inverse transformed pilot signal produced by the first inverse code transforming means is integrated in the particular processing gain time period corresponding to the particular processing gain of the finger unit detected by the control means, to produce an original integration dump value for each particular processing gain;
referential integration dump value producing means for producing a referential integration dump value, which is equal to an integration dump value obtained by integrating the inverse transformed pilot signal produced by the first inverse code transforming means in the referential processing gain time period corresponding to the referential processing gain, from the original integration dump value produced by the integration dump means for each referential processing gain time period; and
reference signal setting means for setting a reference signal according to the original integration dump value produced by the integration dump means in cases where the particular processing gain corresponding to the finger unit accords with the referential processing gain, setting a reference signal according to the referential integration dump value produced by the referential integration dump value producing means in cases where the particular processing gain corresponding to the finger unit is lower than the referential processing gain and it is judged by the frequency error assuming means that the original frequency error is larger than the referential frequency error, and setting a reference signal according to the original integration dump value in cases where the particular processing gain corresponding to the finger unit is lower than the referential processing gain and it is judged by the frequency error assuming means that the original frequency error is equal to or smaller than the referential frequency error, wherein the inverse transformed data signal produced by the second inverse code transforming means is demodulated by the demodulating means while performing a synchronized phase detection for the inverse transformed data signal according to the reference signal set by the reference signal setting means to produce the finger demodulation symbol corresponding to the finger unit.
In this spread spectrum communication apparatus, a reference signal set by the reference signal setting means is used for each finger unit to perform a synchronized phase detection for the inverse transformed data signal when the inverse transformed data signal is demodulated by the demodulating means.
In cases where the particular processing gain of the output data allocated to the finger unit accords with the referential processing gain, the reference signal is set according to an original integration dump value which is obtained by integrating the inverse transformed pilot signal in the particular processing gain time period corresponding to the particular processing gain.
In contrast, in cases where the particular processing gain is lower than the referential processing gain, a referential integration dump value equal to an integration dump value obtained by integrating the inverse transformed pilot signal in the referential processing gain time period is produced from the original integration dump value by the referential integration dump value producing means. Thereafter, in cases where the original frequency error is larger than the referential frequency error, the reference signal is set according to the referential integration dump value. Also, the reference signal is set according to the original integration dump value in cases where the original frequency error is equal to or smaller than the referential frequency error.
Accordingly, the inverse transformed data signal can be demodulated while performing a synchronized phase detection for the inverse transformed data signal according to the reference signal regardless of whether the change of noises or fading in the propagation path is large.
It is also preferred that the channel information transmitted from the spread spectrum transmitting apparatus include data format information indicating a processing gain in- of the output data of each data channel and finger allocation information indicating the particular data channel allocated to each finger unit, and the particular processing gain time period of each finger unit be adjusted according to the channel information in cases where the processing gain of the output data of the particular data channel allocated to the finger unit is changed or the particular data channel allocated to the finger unit is changed.
In this spread spectrum communication apparatus, even though the processing gain corresponding to one finger unit or the particular data channel allocated to one finger unit is suddenly changed by the transmitting apparatus, because the changing information is indicated in data format information or the finger allocation information of the channel information, the original frequency error can be reliably assumed in a new processing gain time period by the frequency error assuming means, so that the synchronization with the output data allocated to the finger unit can be stably held.
It is also preferred that the synchronization holding means of each finger unit comprise:
phase error calculating means for calculating a phase error between the output data of the particular data channel, which is allocated to the finger unit and is received in the spread spectrum receiving apparatus, and the output data of the particular data channel prepared by the spread spectrum transmitting apparatus in the particular processing gain time period of the finger unit;
lock detecting range setting means for selecting a particular lock detecting range from a plurality of lock detecting ranges according to the frequency error assumption information output from the frequency error assuming means and the particular processing gain of the finger unit;
lock detecting means for checking whether or not the phase error calculated by the phase error calculating means is within the particular lock detecting range set by the lock detecting range setting means, outputting a lock detecting signal, indicating that the synchronization with the output data of the finger unit is held, in cases where the phase error is within the particular lock detecting range, and outputting a lock detecting signal, indicating that the synchronization with the output data of the finger unit is not held, in cases where the phase error is out of the particular lock detecting range; and
loop filtering means for producing the synchronization timing signal according to the phase error calculated by the phase error calculating means, wherein the piece of output data of each data channel received in the spread spectrum receiving apparatus is composed of a plurality of incoming data waves corresponding to a plurality of phase offsets, a specific phase offset corresponding to a specific incoming data wave having the highest electric power among electric powers of incoming data waves of a plurality of remaining phase offsets other than one or more particular phase offsets allocated to the finger units is selected from the remaining phase offsets under the control of the control means in cases where the lock detecting signal, indicating that the synchronization with the output data of the finger unit is not held, is detected by the control means, and the specific incoming data waves of the same particular code channel as that allocated to each finger unit is allocated to the finger unit in place of a particular incoming data wave of the particular phase offset.
In this spread spectrum communication apparatus, even though the receiving apparatus fails in the holding of the synchronization with a particular incoming data wave of a particular data channel allocated to one finger unit, a plurality of specific incoming waves of a specific phase offset other than the particular phase offsets allocated to the finger units are newly allocated to the finger units on condition that the specific incoming waves of the specific phase offset are highest among those of phase offsets other than the particular phase offsets. Accordingly, the holding of the synchronization with the specific incoming wave is immediately obtained in the finger units because the electric powers of the specific incoming waves of the specific phase offset are highest, so that the synchronization with the output data can be reliably held in the finger units.
The third object is achieved by the provision of a spread spectrum communication apparatus comprising:
code generating means for generating a plurality of distinguishing codes respectively allocated to a code channel;
redundant data adding means for adding redundant data determined to an input data string to produce a redundant data added input data string;
symbol puncturing means for performing a symbol puncturing operation for the redundant data added input data string produced by the redundant data adding means, to produce a string of punctured symbols;
interleaving means for rearranging either the string of punctured symbols produced by the symbol puncturing means or the redundant data added input data string produced by the redundant data adding means for each prescribed time period to produce a string of interleaved symbols;
transmission data producing means for producing one or more strings of transmission symbols from the string of interleaved symbols produced by the interleaving means, the string of punctured symbols produced by the symbol puncturing means or the redundant data added input data string produced by the redundant data adding means on condition that the number of strings of transmission symbols is determined according to an importance degree of the input data string and the data speed of the input data string;
modulating means for modulating each of the strings of transmission symbols produced by the transmission data producing means at a modulation type determined according to the importance degree of the input data string and the data speed of the input data string to produce one or more strings of modulated symbols;
code channel producing means for performing a code transformation for each of the strings of modulated symbols produced by the modulating means with one distinguishing code generated by the code generating means to produce one or more strings of distinguishable modulated symbols respectively corresponding to one code channel on condition that each string of distinguishable modulated symbols corresponding to one code channel is distinguishable from the strings of distinguishable modulated symbols corresponding to the other code channels;
amplifying means for amplifying each string of distinguishable modulated symbols produced by the code channel producing means with a gain determined for the corresponding string of modulated symbols;
multiplexing means for multiplexing the strings of distinguishable modulated symbols amplified by the amplifying means to produce a string of multiplexed symbols; and
code transforming means for performing a spread spectrum for the string of multiplexed symbols with a spread code sequence to produce a spread spectrum signal and outputting the spread spectrum signal.
In the above configuration, redundant data is added to an input data string if necessary, a symbol puncturing operation is performed for the input data string if necessary, the input data string is rearranged if necessary, and one or more strings of transmission symbols, of which the number is determined according to an importance degree of the input data string and the data speed of the input data string, are produced from the input data string. Thereafter, each of the strings of transmission symbols is modulated at a modulation type (for example, a binary phase shift keying BPSK or a quadrature phase shift keying QPSK) determined according to the importance degree of the input data string and the data speed of the input data string, a code transformation is performed for each of the strings of modulated symbols with one distinguishing code, each string of distinguishable modulated symbols obtained in the code transformation is amplified with a corresponding gain, the strings of distinguishable modulated symbols amplified are multiplexed to a string of multiplexed symbols, and a spread spectrum is performed for the string of multiplexed symbols.
Accordingly, the input data string can be transmitted at a variable data transfer rate and a high quality while using one or more code channels determined according to the importance degree of the input data string and the data transfer rate of the input data string, so that a service of a high speed data transmission at a high quality can be performed as well as a service mainly performing a low speed data transmission such as an audio data transmission.
The third object is also achieved by the provision of a spread spectrum communication apparatus comprising:
a spread spectrum signal transmitting apparatus for producing a plurality of strings of coded symbols from an input data string, producing a string of transmission symbols corresponding to a single code channel or a plurality of strings of transmission symbols corresponding to a plurality of code channels from the strings of coded symbols, modulating each string of transmission symbols to produce a string of modulated symbols corresponding to the single code channel or a plurality of strings of modulated symbols corresponding to the code channels, performing a code transformation for the string of modulated symbols or the strings of modulated symbols to produce output data, preparing channel information indicating information of the single code channel or information of the code channels and transmitting the output data and the channel information;
a spread spectrum signal receiving apparatus for receiving the channel information from the spread spectrum signal transmitting apparatus and receiving the output data transmitted from the spread spectrum signal transmitting apparatus as a receiving signal, the receiving signal being composed of a plurality of incoming waves transmitted through a plurality of propagation paths, the spread spectrum signal receiving apparatus comprising:
searching means for searching the receiving signal for conditions of the propagation paths and producing a searcher detecting signal indicating a plurality of electric powers of the incoming waves;
a plurality of finger units for respectively performing an inverse code transformation for the receiving signal and respectively demodulating the receiving signal to produce a finger demodulated symbol;
channel synthesizing means for synthesizing a RAKE demodulated symbol string from the finger demodulated symbols produced in the finger units;
RAKE demodulated symbol string dividing means for dividing the RAKE demodulated symbol string obtained by the channel synthesizing means into a plurality of strings of divided demodulation symbols respectively corresponding to one string of coded symbols produced in the spread spectrum signal transmitting apparatus;
symbol auto gain control means for calculating an average value of each string of divided demodulation symbols obtained by the RAKE demodulated symbol string dividing means for each of prescribed time periods, dividing each string of divided demodulation symbols by the corresponding average value to produce a plurality of strings of normalized demodulation symbols for each prescribed time period, and performing a gain adjustment for each string of normalized demodulation symbols according to the conditions of the propagation paths detected by the searching means and the channel information to produce a plurality of strings of demodulated symbols for each prescribed time period;
decoding means for performing a decoding operation for the strings of demodulated symbols produced in the symbol auto gain control means to reproduce the input data string; and
control means for allocating the single code channel to the finger units, in cases where the output data produced from the string of modulated symbols corresponding to the single code channel is transmitted to the spread spectrum signal receiving apparatus, according to the channel information, allocating the code channels to the finger units in one-to-one correspondence, in cases where the output data produced from the strings of modulated symbols corresponding to the code channels is transmitted to the spread spectrum signal receiving apparatus, according to the channel information, controlling the finger units, the channel synthesizing means, the RAKE demodulated symbol string dividing means, the symbol auto gain control means and the decoding means according to the channel information and the searcher detecting signal transmitted from the searching means,
wherein a plurality of particular incoming waves having a plurality of particular electric powers higher than the electric powers of the other incoming waves are detected from the receiving signal in the inverse code transformations in the finger units in cases where the output data produced from the string of modulated symbols corresponding to the single code channel is transmitted to the spread spectrum signal receiving apparatus, a particular incoming wave having a particular electric power highest among the electric powers of the incoming waves corresponding to the code channel allocated to one finger unit is detected from the receiving signal in the inverse code transformation of the finger unit for each finger unit in cases where the output data produced from the strings of modulated symbols corresponding to the code channels is transmitted to the spread spectrum signal receiving apparatus, and the particular incoming waves detected in the finger units are demodulated to produce the finger demodulated symbols.
In the above configuration, when the output data is received in the spread spectrum signal receiving apparatus as the receiving signal, conditions of the propagation paths is detected by the searching means.
In cases where the output data produced from the string of modulated symbols corresponding to the single code channel is transmitted to the spread spectrum signal receiving apparatus, the single code channel is allocated to the finger units, a plurality of particular incoming waves having a plurality of particular electric powers higher than the electric powers of the other incoming waves are detected from the receiving signal in the inverse code transformations in the finger units. In contrast, in cases where the output data produced from the strings of modulated symbols corresponding to the code channels is transmitted to the spread spectrum signal receiving apparatus, a particular incoming wave having a particular electric power highest among the electric powers of the incoming waves corresponding to the code channel allocated to one finger unit is detected from the receiving signal in the inverse code transformation of the finger unit for each finger unit.
Thereafter, the particular incoming waves are demodulated in the finger units to produce a plurality of finger demodulated symbols, a RAKE demodulated symbol string is synthesized from the finger demodulated symbols by the channel synthesizing means, a plurality of strings of divided demodulation symbols respectively corresponding to one string of coded symbols produced in the spread spectrum signal transmitting apparatus are produced from the RAKE demodulated symbol string in the RAKE demodulated symbol string dividing means, a plurality of strings of demodulated symbols are produced from the strings of divided demodulation symbols for each prescribed time period in the symbol auto gain control means, and the input data string is reproduced from the strings of demodulated symbols by the decoding means.
Accordingly, even though the output data is produced from the string of modulated symbols corresponding to the single code channel or the strings of modulated symbols corresponding to the code channels according to an importance degree of the input data string and a data transfer rate of the input data string, the particular incoming waves allocated to the finger units can be detected and demodulated, so that the input data string can be reproduced. Therefore, a service of a high speed data transmission at a high quality can be performed as well as a service mainly performing a low speed data transmission such as an audio data transmission.
Also, because a gain adjustment is performed for each of the strings of normalized demodulation symbols respectively corresponding to one string of coded symbols produced in the spread spectrum signal transmitting apparatus according to the conditions of the propagation paths, the reliability for the data demodulation can be improved.
The third object is also achieved by the provision of a spread spectrum communication apparatus comprising:
a spread spectrum signal transmitting apparatus for producing a plurality of strings of coded symbols from an input data string, producing one or more strings of transmission symbols corresponding to one or more code channels from the strings of coded symbols, modulating each string of transmission symbols to produce one or more strings of modulated symbols corresponding to the code channels, performing a code transformation for the strings of modulated symbols to produce output data, preparing channel information indicating information of the code channels and transmitting the output data and the channel information;
a spread spectrum signal receiving apparatus for receiving the channel information from the spread spectrum signal transmitting apparatus and receiving the output data transmitted from the spread spectrum signal transmitting apparatus as a receiving signal, the receiving signal being composed of a plurality of incoming waves transmitted through a plurality of propagation paths, the spread spectrum signal receiving apparatus comprising:
searching means for searching the receiving signal for conditions of the propagation paths and producing a searcher detecting signal indicating a plurality of electric powers of the incoming waves;
a plurality of finger units for respectively performing an inverse code transformation for the receiving signal or an interference removed signal to detect a particular incoming wave and respectively demodulating the particular incoming wave to produce a finger demodulated symbol;
interference replica signal prducing means for detecting an interference signal adversely influencing on the demodulation for the particular incoming waves performed by the finger units from the searcher detecting signal produced by the searching means and setting the interference signal as an interference replica signal;
signal allocating means for allocating the receiving signal directly received from the spread spectrum signal transmitting apparatus or the interference removed signal obtained by subtracting the interference replica signal from the receiving signal;
channel synthesizing means for synthesizing a RAKE demodulated symbol string from the finger demodulated symbols produced in the finger units;
RAKE demodulated symbol string dividing means for dividing the RAKE demodulated symbol string obtained by the channel synthesizing means into a plurality of strings of divided demodulation symbols respectively corresponding to one string of coded symbols produced in the spread spectrum signal transmitting apparatus;
symbol auto gain control means for calculating an average value of each string of divided demodulation symbols obtained by the RAKE demodulated symbol string dividing means for each of prescribed time periods, dividing each string of divided demodulation symbols by the corresponding average value to produce a plurality of strings of normalized demodulation symbols for each prescribed time period, and performing a gain adjustment for each string of normalized demodulation symbols according to the conditions of the propagation paths detected by the searching means and the channel information to produce a plurality of strings of demodulated symbols for each prescribed time period;
decoding means for performing a decoding operation for the strings of demodulated symbols produced in the symbol auto gain control means to reproduce the input data string; and
control means for allocating the code channels to the finger units according to the channel information to detect the particular incoming waves corresponding to the code channels in the finger units, controlling the signal allocating means and the RAKE receiving unit to demodulate the particular incoming wave produced from the receiving signal in each finger unit in cases where the removing of an interference electric power of the interference signal from the receiving signal is not performed, control the interference replica signal prducing means, the signal allocating means and the RAKE receiving unit to produce the interference removed signal and to demodulate the particular incoming wave produced from the interference removed signal in each finger unit in cases where the removing of an interference electric power of the interference signal from the receiving signal is performed, and controlling the finger units, the channel synthesizing means, the RAKE demodulated symbol string dividing means, the symbol auto gain control means and the decoding means according to the channel information and the searcher detecting signal transmitted from the searching means.
In the above configuration, a receiving operation, in which the removing of an interference electric power of the interference signal from the receiving signal is not performed, or a receiving operation, in which the removing of an interference electric power of the interference signal from the receiving signal is performed, is selected. Therefore, the RAKE demodulated symbol string can be obtained after the interference signal removing operation is completed. Also, an interference signal removing operation can be repeatedly performed, and the RAKE demodulated symbol string can be obtained each time one interference signal removing operation is completed.
It is preferred that an interleaving operation be performed for each string of coded symbols in the spread spectrum signal transmitting apparatus to rearranged each string of coded symbols for each interleaving time period, the interleaving time period agree with the prescribed time period, a deinterleaving operation be performed in the symbol auto gain control means for each string of divided demodulation symbols obtained by the RAKE demodulated symbol string dividing means for each interleaving time period, the average value of each string of divided demodulation symbols be calculated in the symbol auto gain control means for each interleaving time period, and each string of divided demodulation symbols, for which the deinterleaving operation is performed, be divided by the corresponding average value to produce a plurality of strings of normalized demodulation symbols for each interleaving time period.
In this spread spectrum communication apparatus, when an interleaving operation is performed for each string of coded symbols in the spread spectrum signal transmitting apparatus for each interleaving time period, a deinterleaving operation is performed for each string of divided demodulation symbols corresponding to one string of coded symbols in the symbol auto gain control means, and a plurality of strings of normalized demodulation symbols are produced for each interleaving time period.
Accordingly, even though an interleaving operation is performed in the spread spectrum signal transmitting apparatus, because the strings of normalized demodulation symbols are produced for each interleaving time period after the deinterleaving operation is performed, when levels of the divided demodulation symbols are changed with time because of an amplitude change based on fading, the interference based on a multi-path communication and/or the interference from signals of other users, levels of the divided demodulation symbols can be made to a constant value.
It is also preferred that one particular string of coded symbols selected from the strings of coded symbols be punctured in the spread spectrum signal transmitting apparatus, and puncture symbols be inserted into puncture positions of one string of divided demodulation symbols corresponding to the particular string of coded symbols in the symbol auto gain control means after the gain adjustment for the string of divided demodulation symbols is performed.
In this spread spectrum communication apparatus, even though the particular string of coded symbols is punctured in the spread spectrum signal transmitting apparatus, puncture symbols are inserted into puncture positions of one string of divided demodulation symbols corresponding to the particular string of coded symbols. Therefore, each string of coded symbols can be punctured in the spread spectrum signal transmitting apparatus, so that a data transfer rate of the output data transmitted from the spread spectrum signal transmitting apparatus can be improved, and the output data can be transmitted at a high speed.